Air Conditioning.
—In addition to the possibility of a constant supply of air, a combination of the exhaust and plenum methods admits of air purification. With such a plant, the air may be washed free from all suspended dust or gases and moistened to any degree of humidity. The process of washing and humidifying air is known as air conditioning. Apparatus for air conditioning is made in a variety of forms to produce any desired extent of air purification and any degree of humidity. The plant may be regulated by hand or it may be made entirely automatic in its action. Air-conditioning plants may be arranged to produce air that is purified, humidified and warmed during winter weather and in summer the hot humid atmosphere may be cooled and dehumidified to a temperature and percentage of moisture that is most agreeable.
Conditioned air is often used in manufactories, not for the purpose of supplying good air to the employees but because of the effect of the atmospheric air on the products. The manufacture of textile fabrics often demands a constant atmospheric humidity in order that the material produced may be uniform in grade; this is particularly true in the making of silks. Various manufactories require an atmosphere free from lint and dust in order that the best quality of material may be produced. The air for ventilation in such places is washed free from all suspended matter before being sent into the building.
In Fig. 173 is indicated an application of apparatus similar in construction to that just described. The arrangement of the parts is such as to produce a Plenum hot-air system of ventilation and temperature regulation.
The plant occupies a room in the basement and the drawing shows the method of heating, together with the plan of distribution. The air duct leading to the room above furnishes an example of the manner of admitting the warmed air to the rooms. The dampers C1, C2, etc., are controlled by separate motors. The motor M is under the control of the thermostat T in the room above. Any change of temperature in the room is corrected by the damper to admit cold or warm air as is desired.
Fig. 173.—Plenum hot-blast heating system with temperature regulation.
The power-driven fan F draws in outdoor air from an opening A, through a set of heater coils H1, in which it is raised considerably in temperature. The heater in this case is a coil of steam pipes. The air—after being warmed—is taken into the fan and from it may be sent through a second set of coils H2, to receive additional heat, or if already sufficiently warmed the air from the fan may pass under the second set of coils and receive no heat from them. Under the first heater coil is also a bypass which may be opened by the motor N to admit cold air that is drawn directly into the fan. The movement of the air through these bypasses is under control of the thermostat, which causes the motor N to open or close the bypass to suit the temperature of the room. When the bypass is opened the steam is shut off from the heater coils.
Examination of the drawing will show that the air from the fan may pass through a second heater H2, to the place marked warm air, or it may pass under the heater to the compartment marked cold air. The amount of warm and cold air which enters the duct is regulated by the position of the dampers C.
The position of the dampers C, which is controlled by the motors M, is made to take amounts of cold or warm air to produce the desired temperature in the rooms. The motors C1, etc., are under control of the thermostat in each room. Any change of temperature in the room will immediately affect the thermostat. The effect on the thermostat will so change the air pressure in the motor that the valve C is moved to correct the difference in room temperature. If warm air is demanded, the motor changes the damper C to close the cold-air supply and take air that must pass through the heater coils H2. If only cold air is desired the damper will turn to shut off the course through the heaters and admit air directly from outdoors.